PFC-Boost+ BUCK Regulator Combo Controller

[TechGuy]

Hi

I am looking to put together an online power supply using a PFC and Buck Regulator with 1000W+ output. A Google search will turn up PFC/PWM off-line combo controllers, using forward or flyback for isolation, which limits the power output to a few hundred watts.

I found this paper from 1998 that discusses a PFC Buck regulator combo:
SINGLE PHASE POWER FACTOR CORRECTION CIRCUIT WITH WIDE OUTPUT VOLTAGE RANGE
http://scholar.lib.vt.edu/theses/pub...erials/etd.pdf

But I was hoping that someone developed a controller implemented this method, But I have not found anything. I suspect there isn't a controller available yet.

Thanks

[eem2am]

i saw the schem on page 15 of your attachment.

its going to be expensive to drive that high side fet.....probably not worthwhile.

For 1000W continuous output power, your best bet is to go for a Continuous mode boost PFC , followed by a Full bridge converter or a phase shift full bridge converter.

....you may need to make the pfc a dual phase boost pfc, to keep individual fet dissipation low.

And realistically speaking, at 1000W, your going to need fans blowing over the fet heatsinks.

...and the boost pfc diode is going to dissipate a lot too, so fans on its heatsink.

i saw the sepic on page 32....looks good but realistically that sepic capacitor is going to be very big and very stressed.

[TechGuy]

Originally Posted by eem2am

i saw the schem on page 15 of your attachment.

its going to be expensive to drive that high side fet.....probably not worthwhile.

Look on page 18. Thye Author has all of the losses listed. 26W for the Buck S1 switch (using a IGBT) and ~30W on the Boost S2 switch and that's for a 2KW circuit. I would imagine replacing the IGBTs with Mosfets would reduce switching losses.

Why do you say "expensive to drive that high side fet"? An H-bridge uses two high side transistors. Buck Regulators are typically 95% efficient.

Originally Posted by eem2am

For 1000W continuous output power, your best bet is to go for a Continuous mode boost PFC , followed by a Full bridge converter or a phase shift full bridge converter.

....you may need to make the pfc a dual phase boost pfc, to keep individual fet dissipation low.

Still going to have PFC switching losses. I would think the Buck switching losses would be lower than a full bridge converter. My thought was this design would have less loss than a PFC + Full bridge converter, since there are fewer overall switching components.

The disadvantage is its not isolated and the regulation would not be as tight since a continuous PFC boost would charge the caps a higher voltage, providing more ride-through energy to be consumed near the AC Zero crossing point. Am I missing something else?

Originally Posted by eem2am

i saw the sepic on page 32....looks good but realistically that sepic capacitor is going to be very big and very stressed.

The author also dismissed sepic as an option.